1. Industrial Field of the Invention
The present invention relates to an improvement of a bicycle frame, and more particularly, to a damper mechanism of the bicycle frame.
2. Description of Related Art
As for absorption of shocks caused during running of a bicycle, there have been conventionally proposed various techniques of weakening the shocks by bending front forks of a bicycle frame. A suspension mechanism has not hitherto been used in the bicycle. This is because the use of the suspension mechanism conflicts with demands of weight reduction and high rigidity which are fundamental requirement for the bicycle.
In recent years, weight reduction of the material has succeeded for component parts of the bicycle more and more. A rider requires a comfortable feeling when he rides on the bicycle. With the commercial spread of mountain bicycles (MTB), various kinds of races such as off road running, down-hill running and so on have been extensively carried out. Thus, there occurs a serious demand for absorbing shocks caused during running of the bicycle on a rough road surface.
Nowadays, there are developed bicycles including various types of shock absorbing technique in which: 1/ shocks are absorbed by front forks located on the side of a front wheel or a urethane reinforced resin material is incorporated in its head portion; 2/ a saddle is provided with a suspension; and 3/ small-sized shock absorbers are disposed between a mono-seat lug and a top tube pivotably around a seat lug (USSN 07/980281).
In the above-described structure in which the shocks are absorbed by the front forks on the side of the front wheel or the urethane reinforced resin material is incorporated in the head portion, or the saddle is provided with the suspension, however, the shocks are absorbed on the side of the front wheel or at the saddle portion, and a satisfactory shock absorption effect cannot be obtained. There has been developed no bicycle with a damper mechanism having a shock absorbing ability on the side of a rear wheel which is regarded as the most important matter in terms of a function and a feeling of riding of the rider during running of the bicycle, while maintaining a high rigidity. The shock absorbing ability of the conventional damper mechanism is extremely unsatisfactory, particularly in case of off road running.
Also in the shock absorbing technique in which the small-sized shock absorbers are interposed between the top tube and the mono-seat lug pivotably around the seat lug, the mechanism is complicated in structure, inferior in design, increased in weight and manufactured at a high cost, and therefore it is not satisfactory in practical use.